And her early performances Down Under did little to dissuade public opinion as she cruised to the title in Brisbane before waltzing through her opening engagements in Melbourne. However, her hopes of picking up the Daphne Akhurst Memorial Cup for a sixth time came to a shuddering halt against Sloane Stephens in the quarterfinals.

Stephens, who had pushed her fellow American during a straight set loss in Brisbane three weeks earlier, had made all the right noises before the match and was true to her word once out on court. Calm and composed from the word go, she won her first three service games without dropping a point, more than holding her own in the baseline exchanges and retrieving brilliantly.

Despite losing the opening set, the teenager resisted any temptation to depart from her aggressive game plan, and her positive approach began to reap dividends as the contest wore on.

With Williams struggling to subdue her inspired opponent and shake off a back injury, Stephens capitalized to force a third set. So often at her most dangerous with her back to the wall, Williams rallied in the decider, but Stephens continued to come up with all the right answers.

In fact, it was Williams that stuttered as the match approached its climax, committing a raft of uncharacteristic errors as she served to stay in the match at 5-4 down. Down the other end her compatriot remained as unflappable as ever, closing out a 36 75 64 win to book a semifinal with Victoria Azarenka.

"I definitely improved a lot since last year," Stephens said. "Definitely last year it was all new to me and I was just kind of taking it all in. It was the first time playing her in Brisbane, so it was tough. But the first time you do anything it's tricky. I think I was kind of just ready to play this time and I was just enjoying myself."

Her unexpected triumph catapulted Stephens from young pretender to Grand Slam contender and also saw her win over a few new fans. "John Legend tweeted me. Dirk Nowitski tweeted me," Stephens, whose Twitter followers more than doubled during her two hours on court, added. "I'm just excited - I always wanted John Legend to sing at my wedding and now I'm like, 'Oh, my God. He tweeted me.'"